1. Field of the Invention
The present invention relates to a document feeding apparatus and more particularly relates to a document feeding apparatus for supplying a document from a paper feeding tray on a platen glass of an image processing apparatus such as an electrophotographic reproducing machine and an image scanner, reading an image of the document on the platen glass, and then delivering the document to a paper delivery tray.
2. Description of the Prior Art
It is publicly known to use a document feeding apparatus so-called as an automatic document feeder (ADF) in order to supply automatically a document to a document reading portion in an image forming apparatus such as an electrophograhic reproducing machine.
The necessity of a document feeding apparatus capable of processing dual-surface documents has been recently increased.
Such a dual-surface document feeding apparatus is described in the Japanese Patent Laid-Open No. 175279/95, for example. The document feeding apparatus has first and second modes. In the first mode, a one-sided document is delivered directly to a paper delivery tray after one side surface of the document is read. In the second mode, a dual-surface document is once fed through a document feeding path to the paper delivery tray after a first surface of the document is read, returned from the paper delivery tray, and then fed again to the document feeding path through a duplex feeding path. Then, the dual-surface document is fed again to the paper delivery tray after a second surface of the document is read, returned from the paper delivery tray, fed again to the document feeding path through the duplex feeding path, and delivered to the paper delivery tray so that the dual-surface documents are stacked one by one on the tray in regular sequence in page order, with the first surface of the documents on the underside. Specifically, the dual-surface document is circulated by a roller for delivering the document to the entrance of the paper delivery tray and for reversing the inside and outside of the document, and by the duplex feeding path for feeding the document from the paper delivery tray to the document feeding path. Further, the dual-surface document is reversed by said roller, and delivered to the paper delivery tray by said roller through a path which has been used for the document whose second surface is read.
However, in the conventional document feeding apparatus as mentioned above, the document must be passed three times through the document reading portion, if the document is a dual-surface document and the documents are stacked one by one on the paper delivery tray in regular sequence in page order. In this case, in the last time of the passing of the document, the document must be passed through the reading portion in spite of the fact that it is not necessary to read the document at the reading portion. As a result the document reading portion becomes dirty, errors occur in image reading, and cleaning of the document reading portion is required frequently.
Further, the document must be passed through the document reading portion after the reading of the document has been completed, and no succeeding document can be fed, so that the processing time of the dual-surface document cannot be shortened.
Furthermore, in such a conventional document feeding apparatus, the paper delivery tray is arranged directly below the paper feeding tray, and the documents are delivered to the same paper delivery tray irrespective the document size, so that a document of short length delivered on the paper delivery tray may be difficult to find because the document is hidden by the paper feeding tray. In addition, the document may be hard to take out because the document is covered by the paper feeding tray.
Japanese Patent Laid-Open No. 59466/83 discloses a document feeding apparatus having two paper delivery trays arranged up and down, wherein an interruption copied document is delivered to an extra paper delivery tray. However, this document feeding apparatus has such a problem that the recognition and taking out of the document delivered to the paper delivery tray of the lower stage are disturbed by the paper delivery tray of the upper stage.